The boot option is "gfx=auto" (on hd: "rw gfx=auto"). When you use the Special ISO then grub menu has got lots of Kanotix (gfxboot) entries in Live mode. I dont see a huge problem to select em. If you already hd installed as root (use su):

You can use a custom config, just name it xorg.conf.nvidia or when you switch between other nvidia cards more often and you want to use that config just for this specific card call it xorg.conf.vvvvdddd where vvvv is the vendor id and dddd the device id in lowercase.